For the production of Pleurotus mushroom according to the method in bags, it has been customary in the past to pasteurize a substrate, inoculate it with spawn seeds, transfer the mixture into the plastic bags, and after a suitable method of incubation, to collect the mushrooms at maturity. The inoculation is performed by mixing the substrate and the fungus seeds of Pleurotus in the open air. This operation also requires for the pasteurization room to remain open for several hours. Moreover, since it is highly desirable to prevent contamination from contact with microbial propagules in the air, the transfer of the inoculated pasteurized substrate from one container to plastic bags involves some difficulty and some contamination are always involved.
The closest known prior art is U.S. Pat. No. 2,851,821 wherein spawn is grown in a plastic bag. The bag is closed by turning the ends of the bag in, forming a chimney and it is sealed by placing a wad of cotton or the like in the chimney thus formed. In another embodiment, a tube is inserted in the top of the bag and the bag gathered around the tube with a string. A filter plug is then placed in the tube.
Another method is described in U.S. Pat. No. 4,027,427 wherein the spawn is grown in a plastic bag provided with a temporary filter cover. This bag is provided with a removable closure means for filling the bag and maintaining sterility during the processing steps.
Both U.S. Pat. Nos. 2,851,821 and 4,027,427 are only related to the aseptic preparation of mushroom's spawn in a plastic bag and can not be applied for the actual mushroom production in a pasteurized substrate. Moreover, in both cases the substrate is sterilized rather than pasteurized.
If, this plastic bag was to be used for the purpose of the present invention, it could only contain 2 to 3 kg of substrate. Because it is so small, it could only be inoculated at one point (from the top), which would lead to an asymmetric distribution of the inoculum and an irregular spawn running. Further, the actual industrial production of the mushrooms requires 20 to 30 kg bags which could not be handled in this way.
Although such a bag prevents the risk of contamination for spawn production, it is not useful for the process of growing Pleurotus. Since Pleurotus fruit grow along the axis, it prefers a bag which permits its fructification along the side of the bag.
Furthermore, the plastic bag for the production of Pleurotus can contain up to 30 kg of substrate and requires a mushroom's spawn that grow faster than the internal bacterial microflora. Thus, it is needed that the spawn running start simultaneously and therefore, the inoculation has to be performed at several different points. The multiple inoculation of the substrate for the production of Pleurotus is so required, because the substrate is in the form of a rigid straw roll and cannot be mixed like the grain spawn to homogenize the inoculum distribution.
Further, the method of mass pasteurization creates differences in the aeration and the moisture within the substrate, leading to variations in yields between the rolls.
Another disadvantage is the number of handlings of the substrate. The substrate is twice handled, when placed into the chamber, and when inoculated.
Thus, it would be desirable to find a process which can enable the inoculation of the substrate without risking any contamination and permitting the mushroom growth along the horizontal axis.
It would also be highly desirable to have a plastic bag provided with perforations which would easily permit the mushroom fructification. This would results in a mushroom's shape of premium quality.